Electrical hand-held power tools, such as, for example, impact screwdrivers, drills, angle grinders, jigsaws, circular saws or planers for use by skilled workers or do-it-yourselfers usually include either an AC motor or a DC motor as the drive motor. While the former is generally supplied with AC current from the power supply network via a power cord, the electrical energy for supplying the DC motor generally originates from a so-called rechargeable battery pack, a rechargeable accumulator in a housing which is coupleable to the housing of the hand-held power tool and which is electrically connected to the power supply lines of the DC motor when the two housings are coupled.
Rechargeable battery packs may include rechargeable accumulators, generally a plurality of battery cells connected in a parallel and/or series circuit. Herein, a rechargeable battery pack is therefore understood to be an accumulator pack which is preferably made up of several electrically interconnected battery cells and may store electrical energy, which delivers the energy necessary for the operation of the hand-held power tool, and is exchangeably accommodated in a chamber, an interface, or the like of the hand-held power tool. The electrical contacting takes place mostly in the area of a locking device.
Conventional charging devices for rechargeable battery packs may include a charging electronics system which is situated in a housing and includes a receptacle for a rechargeable battery pack to be charged and an interface situated in the area of the receptacle and includes contact elements for contact elements of the rechargeable battery pack. The electrical recharging of a rechargeable battery pack is possible with the aid of such charging devices.
Furthermore, in conventional tool systems may, either one type of rechargeable battery pack may be utilized with many different hand-held power tools or, conversely, one hand-held power tool may be operated with the aid of different types of rechargeable battery packs. In this case, it may be important, in principle, that the hand-held power tool and/or the charging device have information regarding the rechargeable battery pack, such as, for example, the maximum charging and discharging current, the present operating temperature, and/or the internal resistance of the rechargeable battery pack. Present-day rechargeable battery pack systems are controlled by management systems, which monitor the cells and regulate the charging and discharging current. The objective of such conventional methods is always to extend the service life of the rechargeable battery pack under consideration of the system parameters of the rechargeable battery system, almost all noteworthy manufacturers of power tools generally offering their own charging technology for their rechargeable battery packs, so that both the charging devices as well as the hand-held power tools are specially configured for the geometry and power data of the rechargeable battery pack offered by the manufacturer.
Different conventional systems provide the hand-held power tool and/or the charging device with the required information regarding the installed rechargeable battery pack. In this way, an electrical coding is installed, for example, in the rechargeable battery pack itself with the aid of coding resistors, which are measured by the hand-held power tool and/or the charging device. Coding resistors have the disadvantage that one additional contact per resistor is generally necessary between the hand-held power tool and/or the charging device and the rechargeable battery pack. This has the disadvantage that the electrical coding with the aid of resistors only allows for a limited number of codings, whereby a future compatibility is limited, since the corresponding parameter sets must be established in the reading-out device during manufacture. If such a resistor is corrupted, e.g., due to damage resulting from ESD, an increased transfer resistance at the contact, or contaminations, a misinterpretation of the coding element by the hand-held power tool and/or the charging device is possible, so that, for example, charging may not be carried out with the maximum permitted current, whereby a longer charging time is required, or the maximum permitted current may not be discharged, whereby the tool operates using reduced power. Furthermore, due to limited measuring accuracy, only a limited number of different coding resistors are distinguishable in the hand-held power tool and/or the charging device.
Such a system is highly cost-effective, and it was therefore frequently utilized in the past, and whereby many tool systems including a hand-held power tool and/or a charging device and a rechargeable battery pack which utilize this technology, are presently available on the market.
Alternatively, the interface between the rechargeable battery pack and the hand-held power tool and/or the charging device may be a digital interface, e.g., a single-wire interface, in which an electrical coding also lies at high potential via a data bus and/or via a pull-up resistor, and is pulled to ground by the communication partners in accordance with the bus protocol definition. In this case, the hand-held power tool and/or the charging device exchange the required information with the rechargeable battery pack via an additional data contact and with the aid of established transmission protocols. The bus system improves the disadvantage of the electrical coding via resistors, since the rechargeable battery pack may also transmit parameter values which are not known in advance. The bus system has the disadvantage, however, that additional contacts are still required, and the rechargeable battery pack also requires a separate intelligent electronics system. Such rechargeable battery packs may automatically gather data during use, for example, regarding the number of charging cycles. Although these data may be helpful during diagnosis in the event of an error, digital interfaces are technically more complex, since they require an intelligent electronics system on both sides. Furthermore, which data are stored is already established during the manufacture of the rechargeable battery pack. This specification may not be changed at a later time.
In the case of the aforementioned systems, it may be disadvantageous, in particular, that a hand-held power tool and/or a charging device and/or a rechargeable battery pack including a digital interface is not compatible with a conventional rechargeable battery pack, which includes a mechanical or electrical coding with the aid of coding resistors.